🚀 go-pugleaf

This document by Becker and Chambers came out in March of this year.
It and the soft-cover Wadsworth book superseed the original 1981 manual
for the S system.  I can hardly review it, as Mike Meyer just dropped
a copy in my lap, but it seems more readable than the original manual.
It is designed for writing new functions.

There are some nice things like a list of the graphics routines and
stat utilities used by some of the routines, so that you can easily
write some graphics or stat functions.

Device driver writers will not find a whole lot, but it is better
organized.  However, many answers remain burried in the code.  For
instance, I happened to find out that the "device code number",
am(30), is the flag for turning deferred graphics on/off at
initialization, by snooping in the code.  Also, you will still
have to wade thru the code in ~s/src/graph/grz to
figure out how to do "high-level" things like writing your own
zlinsz() routine or doing ztextz() for you fancy terminal.